[Moonfly]

I figured I would start a thread that helps people who want to build their own sub. There are a few common questions that crop up and hopefully this can be a place people can come for help getting these answers.

I'm not the most knowledgeable person in the world so Im hoping other people will come in here and help out too.

I'll start off though by adding the following link:

Audio Innovation - by Dan Marx www.danmarx.org

IMO, this is the very first step down the DIY route and the perfect start point.

Here's hoping others jump in with useful info and links

Edit: if people want to add further links then feel free, or PM your links to me and I'll add them into the relevant posts of mine. Hopefully we will have a complete step by step guide on how to build your own sub from start to finish.

Cheers

[Moonfly]

Ok so after you have decided on which sub woofer design is for you, its time to find something to put in it. This means a driver and amplifier. I'll start off with the driver, as this is the harder of the 2 parts to figure out.

The search for a driver starts with looking into the T/S (Thiele Small) parameters of the driver. These are a group of electrical and mechanical properties of the driver, and they basically tell you how the driver will act, what size enclosure it will work best in, and generally if the driver is the right one for your needs. A good explanation of these parameters can be found here:

Thiele/Small - Wikipedia, the free encyclopedia

and

LoudspeakerBuilder.ca - (Thiele-Small Parameters)

I found the main parameters of interest for me (starting out for the first time) were the Fs, Vas, Xmax, Z and Pe.

• FS - this is the frequency the speaker naturally wants to work at. If you want lower bass, look for lower fs, if you want more focus on higher frequency audible bass and arent as worried about depth aim higher.
• Vas - this can be used as a sort of guide to the size of cabinet the speaker best works in, and this is important, especially if box size is important to you. Very generally speaking, a higher Vas figure means you'll need a larger cabinet, although the Vas figure itself is actually a measure of the drivers stiffness, not required box size.
• Xmax - this is the limit if movement (usually in mm) the driver is capable of before serious distortion occurs. Sometimes this is from rest to maximum excursion (known as one way xmax), but can also be its max in to max out (known as peak to peak, or P-P). Its important to monitor this when designing your sub in simulation software. Its also important to get this figure correct both when modelling and when gathering your driver data.
• Z - this is the impedance ohm rating of the driver, and this info is needed when choosing what amp to use to drive your speaker and vice versa. It can also be important when working out loadings for multiple driver applications.
• Pe - this is the watt rating the driver can handle, basically the thermal power handling of the motor. This too is important when your choosing an amp to drive the speaker, and running models in software simulations etc.

There are more parameters, and you need these when using software to model your drivers. You can usually find all this information from the website of driver suppliers, or ask them if you cant find the info.

Once you think you have a good driver that suits your needs, you can model it in software that is free and readily available to see how it will work. From this you will be able to get an idea of how the driver works, in your chosen enclosure, and be able to see if your likely to achieve your goals.

There are some free software programs that are available to run your simulations, the one Ive been using is this:

Win ISD by linear team

Using this program (or a similar one), and the drivers TS parameters you can get a good idea of how the sub will perform. You can see how loud and how low your sub is likely to go, as well get a good idea of how large your box needs to be to achieve your goals.

Hopefully this will help choose the right driver for what ever enclosure type you decided on.

[Moonfly]

So you now have a good idea of what style sub you want to build, and should have decided on your driver. This means you now need to choose how to power your new sub.

There are a couple ways you can do this, one is to by an amp designed to power a sub. Usually this is a plate amp, and there are various places you can buy these. An example of a good one is this:

O Audio - 500W BASH Subwoofer Amplifier

or any of these

http://www.bkelec.com/Modules/Sub_Bass.htm


These amps are a good option, but finding ones with more power if you need it is difficult, and compared to option 2, rather expensive.

Option 2 is the one Ive opted for. A sub woofer is a speaker like any other, and simply needs an amplifier to drive it. For this you can use any suitable amp and it doesnt have to be a dedicated subwoofer plate amp. The amp I have opted for is one of these:

BEHRINGER: EP4000

This is a standard amp, and this particular one is designed for high power applications like powering large speakers at clubs or venues etc. Its good for powering a sub as its got a lot of power, is designed for high power extended use and best of all, its cheap. Lower power models are available and are cheaper, and other amps are available, but this is a good example of the kind of thing you can use for your DIY project. Besides being cheap, there is also the advantage of huge amounts of power, so if your a bass nut wanting to power multiple drivers, then these really become the only serious option.

As a side note, I have decided to keep my amp external. This means I will connect the amp to the sub using normal speaker wire, and the amp will be kept in my rack. On the sub enclosure I will seat one of these for connecting it up:

Gold Plated Binding Posts : Connectors : Maplin

This method is not compulsory, but its also a viable option as well so worth keeping in mind. One of the advantages of this method is it makes it easier to calculate the size of your box, and makes it easier to design and construct, good for first timers. It also makes it easy to swap and change your amp if you decide to upgrade in the future etc.

[Moonfly]

At this point, you should have a good idea of what type of sub you want to build, what driver or drivers your going to put in it, and how your going to power it. The next step is to start designing the box.

For the box, you need to consider the style of box you want, cylinder or box type or even triangular boxes, and ported or sealed etc. There are various arguments as to which is best, and those that say it makes no difference, so basically take your pick, it just a personal choice. The software will have given you a recommended enclosure size, usually in litres. There is a very useful tool for working this out, and linking this will be frowned upon but AFAIK there isnt a better tool for the job:

Enclosure Volume Calculator (EVC)

This will help you work out the dimensions of your box, and can take account for lost box volume due to driver displacement, porting, and bracing. You should now have all you need to start building your sub, which means its time to start looking at materials, fixings, construction and finishing.

At this point I'll now leave this thread open to discussion. If there is anything further anyone wishes to ask I think this would be a good place, and hopefully plenty of useful info on the practical side of the construction process will build up for fellow enthusiasts

[Pollywoggle]

Well done Moonfly for taking the trouble to post this info, I wish I didn't have skill deficiency disorder, I would so love to build my own sub!

[m4rky_m4rk]

+1 ... well done MOONFLY

Just one thing... IB's are not part of your considerations...just boxed subs. So someone else will have to put up the case for IB's. I will not mention any names this time as to who might have the necessary expertise to say why an IB should be considered! Some on here may have the choice of a box or IB's.

[MI55ION]

I for one would love to have an IB installation but somehow don't see it taking off in this country, not till the majority can enjoy the luxury of fully detached houses or cinema buildings.

I must admit all this talk of diy subs has brought back a few memories of my ICE days and certainly renewed interest.

I blame a few of you here for this so don't be surprised if I come back soon asking all sorts of elementary questions.

Moonfly, Russ, Graham hope you guys are taking plenty of pics to document those sub builds.

[Moonfly]

Originally Posted by m4rky_m4rk

+1 ... well done MOONFLY

Just one thing... IB's are not part of your considerations...just boxed subs. So someone else will have to put up the case for IB's. I will not mention any names this time as to who might have the necessary expertise to say why an IB should be considered! Some on here may have the choice of a box or IB's.

Well an IB is basically a large sealed sub. There are specific IB drivers which are easy enough to find on google. The vas of these drivers is much greater than that of nomal drivers, so its a case of calculating the volume of the room that will act as the enclosure and then installing the correct number of drivers. This should be a case of dividing the volume of the room by the vas of a single driver.

The EVC I linked earlier will make working out room volume much easier, and the amp Im using that is also linked is commonly used for IBs. Usually an IB will use a minimum of 4 x 15" drivers or 2 x 18" drivers. Nimby's sig link is the best route for that I think, or perhaps he will chip in here

[Nimby]

You've got most of it covered but just for clarity:

Find the Vas for a single IB driver.

Multiply by the number of drivers for Total Vas.

Then multiply Total Vas by 10 for the smallest enclosure size you can safely get away with. The enclosure can be fairly leaky except around the drivers.

If you don't have that much room then the smaller volume will force up the driver's natural Fs. It will also increase the pressure loads on the enclosure walls and may demand better sealing.

The bass output is the same on both sides of the wall, ceiling or floor which you use as your infinite baffle.

Use an opposed driver manifold to cancel vibration rather than using the far more risky array.

Many examples are shown in The IB Cult forum galleries together with truly encyclopaedic FAQs.

[Pollywoggle]

I was looking at triangular steel tube bracing filled with sand that someone is using to prevent flexing in the States, IB is a whole different world if you have the space and no nearby neighbours

[Russell.Williams]

Here's a useful article from Tom Nousaine on the art of tuning enclosures with stuffing.

The jist is go smaller and tune the enclosure into being effectively larger (by up to 30%) using fibre fill. The opposite route of going too large and then reducing the completed box's volume would obviously be harder.

Russell

[AngelEyes]

Russ pointed me at this useful alternative to WinISD: UniBox - Unified Box Model for Loudspeaker Design - Kristian Ougaard


Mod Edit: that link is down at the moment this one seems to be working:

http://go.avforums.com/?id=223X354&u...2Fubdwnld.html

DAve

[IronGiant]

Originally Posted by Russell.Williams

The opposite route of going too large and then reducing the completed box's volume would obviously be harder.

Russell

I'm afraid I'd have to disagree there Russell

[Russell.Williams]

I deplore the use of such an inefficient damping medium.

Russell

[AngelEyes]

That surprises me from a man that extols the virtue of sorbothane, a
material renowned for it's excellent damping characteristics and designed to mimic human flesh I believe?

Surely Dave is on to something here?

Adam

[podyperson]

Originally Posted by Moonfly

So you now have a good idea of what style sub you want to build, and should have decided on your driver. This means you now need to choose how to power your new sub.

There are a couple ways you can do this, one is to by an amp designed to power a sub. Usually this is a plate amp, and there are various places you can buy these. An example of a good one is this:

O Audio - 500W BASH Subwoofer Amplifier

or any of these

BSB


These amps are a good option, but finding ones with more power if you need it is difficult, and compared to option 2, rather expensive.

Option 2 is the one Ive opted for. A sub woofer is a speaker like any other, and simply needs an amplifier to drive it. For this you can use any suitable amp and it doesnt have to be a dedicated subwoofer plate amp. The amp I have opted for is one of these:

BEHRINGER: EP4000

This is a standard amp, and this particular one is designed for high power applications like powering large speakers at clubs or venues etc. Its good for powering a sub as its got a lot of power, is designed for high power extended use and best of all, its cheap. Lower power models are available and are cheaper, and other amps are available, but this is a good example of the kind of thing you can use for your DIY project. Besides being cheap, there is also the advantage of huge amounts of power, so if your a bass nut wanting to power multiple drivers, then these really become the only serious option.

As a side note, I have decided to keep my amp external. This means I will connect the amp to the sub using normal speaker wire, and the amp will be kept in my rack. On the sub enclosure I will seat one of these for connecting it up:

Gold Plated Binding Posts : Connectors : Maplin

This method is not compulsory, but its also a viable option as well so worth keeping in mind. One of the advantages of this method is it makes it easier to calculate the size of your box, and makes it easier to design and construct, good for first timers. It also makes it easy to swap and change your amp if you decide to upgrade in the future etc.

At last thanks to you I have absolute proof I can use an external amplifier(Crown 1500) to power my Krix passive sub woofer,I am in heaven you sir are a legend.

[Moonfly]

Glad the thread is of use to people

In the US people build many more DIY subs than in the UK, and they pretty much all use external pro amps. They are affordable amps offering much larger power supplies than plate amps generally do. Just check in the spec of the amp you intend to use that it goes down to a good frequency, below 20hz. Many pro amps do, but some roll off heavily at around 20hz.

[Coll]

Hi Moonfly I have a couple of questions for you regarding subs.
1 Do you know if the Win ISD programme is for damped or undamped cabinets.
2 What is your opinion of Dayton subwoofer drivers

[Moonfly]

1) I assume you mean damped in terms of adding wadding or foam lining, in which case its undamped.
2)They are decent drivers offering a good balance between good performance for a good price. Not the very best drivers, but then they arent the most expensive. I would certainly use those drivers if their cost was what I was aiming to spend without hesitation. That said, the Fi SSD drivers are on a par and available from a UK direct distributor, so personally I would opt for the SSD range over Daytons purely for that reason, and ther fact there is probably nothing to choose between them.

[Coll]

Can you say who the Distributor is for Fi SSD and also who you think makes the best drivers for Subs

[batfink007]

Originally Posted by Coll

Can you say who the Distributor is for Fi SSD and also who you think makes the best drivers for Subs

UK distributor is bladeice.com

[Moonfly]

Originally Posted by Coll

Can you say who the Distributor is for Fi SSD and also who you think makes the best drivers for Subs

Who makes the best drivers will always be up for debate. TC sounds claim they make the best driver, and its hard to ignore their claims as the drivers are very expensive and have a lot of technology involved. Thing is, for half the price or less you can have 75% of the performance, and taking Fi as an example, a pair of Fi Q18's will outperform a single LMSU for about 2/3's the cost, albeit it in a larger cabinet.

A few companies make very good drivers, Dayton included. Mach 5 Audio, Peerless (in europe), CSS, TC sounds, and Fi all make very good drivers that will compete with anything in the commercial world. I use Fi at the minute because they are the only high end driver manufacturer with a dedicated UK distributor. Peerless make decent drivers, but they arent on the same level as the Fi SSD and Q series. JBL make budget drivers and for the money offer cracking performance.

Like I say though, I only use Fi because IMHO, they make the best drivers that are readily available to us at high VFM prices. I can only get similar or better drivers by spending more and ordering direct from the US, which can be fraught with its own problems.

[hoppaz]

Can I ask what makes the Fi drivers so good?

Having checked their specs they seem to have large magnets, lots of xmas but an Fs is around 30-32hz if I recall correctly. This seems quite high up the scale when other drivers in similar size has Fs of 20-25hz.

[Coll]

Hi Moonfly
I am actually looking for 2 good 10 inch subs. I have looked at the JBL UK website and the prices and specs are good. I assume you are referring to the JBL car subwoofer drivers as I could not find any other drivers

[Moonfly]

Originally Posted by hoppaz

Can I ask what makes the Fi drivers so good?

Having checked their specs they seem to have large magnets, lots of xmas but an Fs is around 30-32hz if I recall correctly. This seems quite high up the scale when other drivers in similar size has Fs of 20-25hz.

Good amount of motor force, high xmax (good linearity), and high power handling basically. The Q series use dual 3" voice coils and a quad spider suspension so they are a heck of a driver really for a fair price. The Fs is higher than some other drivers (the Q were originally designed fro car audio), so they need a bit more eq than some other drivers, like the AE drivers I used for example, but they still perform and the low end output is roughly equal to the AE drivers (most of the eq is used to cut the upper bass). The design is not unlike a lot of the high end drivers you will see, but the main reason I use the Fi's is because they are a high end design, and available directly in the UK. In all the time I spend lookign at drivers as well, most seem to have had an issue here or there with a failed driver or damaged on arrival, but never have I seen an Fi suffer like this, so I also believe their QC department is one of the best in the business, at least from experience.

Originally Posted by Coll

Hi Moonfly
I am actually looking for 2 good 10 inch subs. I have looked at the JBL UK website and the prices and specs are good. I assume you are referring to the JBL car subwoofer drivers as I could not find any other drivers

They are the only ones I am aware of, but I dont use them and havent taken much time to explore JBL's product range. A few people have used them and they are popular amongst people wanting budget drivers.

What is your intended design and budget?

[hoppaz]

Originally Posted by Moonfly

Good amount of motor force, high xmax (good linearity), and high power handling basically. The Q series use dual 3" voice coils and a quad spider suspension so they are a heck of a driver really for a fair price. The Fs is higher than some other drivers (the Q were originally designed fro car audio), so they need a bit more eq than some other drivers, like the AE drivers I used for example, but they still perform and the low end output is roughly equal to the AE drivers (most of the eq is used to cut the upper bass). The design is not unlike a lot of the high end drivers you will see, but the main reason I use the Fi's is because they are a high end design, and available directly in the UK. In all the time I spend lookign at drivers as well, most seem to have had an issue here or there with a failed driver or damaged on arrival, but never have I seen an Fi suffer like this, so I also believe their QC department is one of the best in the business, at least from experience.

Thank you for the info. So it really is about moving air then but without breaking

Oh and I guess a supersize magnet helps make the bass nice and fast?

One last thing I notice the new range of inuke amps (well the 3000) have built in subwoofer settings. Is this a useful feature to have?

[Moonfly]

Originally Posted by hoppaz

Thank you for the info. So it really is about moving air then but without breaking

Oh and I guess a supersize magnet helps make the bass nice and fast?

One last thing I notice the new range of inuke amps (well the 3000) have built in subwoofer settings. Is this a useful feature to have?

Good bass really is about moving air, and doing it cleanly. The more air a driver can shift with ease, the easier it can go low, and doing it with ease it what keeps it clean. A high end single 18 can move more air than 4 10" drivers, and can probably move more air than 6 average 10" drivers.

Are you referring to the DSP versions of the amps. These functions could be very useful as long as you know how to use them properly.

[hoppaz]

Originally Posted by Moonfly

Good bass really is about moving air, and doing it cleanly. The more air a driver can shift with ease, the easier it can go low, and doing it with ease it what keeps it clean. A high end single 18 can move more air than 4 10" drivers, and can probably move more air than 6 average 10" drivers.

Are you referring to the DSP versions of the amps. These functions could be very useful as long as you know how to use them properly.

Yes DSP. I have been doing a bit of research and these new range of amps can be set-up specifically for subwoofers which in my mind makes me think they can focus their energy on producing lower frequencies rather than the full frequency range.

I am more mechanically minded than mathematically minded hence how I can see how sub drivers work and what physically makes them better than others.

I think my next question is relevant to this thread as it refers to running smaller, M&K or bookeshelf type speakers and subs as opposed to running floorstanders and a sub.

Can you get to a point when you oppose two extemes of a sub and speaker (you get a sub that is too big and naturally Fs low and main speakers that are too small and the natural frequency response of the speaker so high that the result is a big gap in the frequency response where the two cross)?

Eq'ing aside I know that if you can create a natually, good full range frequency response it is best way forward.

[Moonfly]

Originally Posted by hoppaz

Can you get to a point when you oppose two extemes of a sub and speaker (you get a sub that is too big and naturally Fs low and main speakers that are too small and the natural frequency response of the speaker so high that the result is a big gap in the frequency response where the two cross)?

You can, but no speakers worth their salt will suffer this problem unless specifically designed as part of a very high end bespoke system. As long as any speakers you buy are good to 80hz your fine.

[hoppaz]

Originally Posted by Moonfly

You can, but no speakers worth their salt will suffer this problem unless specifically designed as part of a very high end bespoke system. As long as any speakers you buy are good to 80hz your fine.

Not sure if there is a mistake in your sig but I keep seeing "RIP -" and knowing what a sensitive subject that is usually associated with I can't help thinking there should be more to it.